linux-kernel - Re: [PATCH RESEND] PCI/AER: Use a common function to print AER error bits

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Date:   Mon, 30 Apr 2018 12:41:26 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        gregkh@...uxfoundation.org, fred@...dlawl.com,
        linux-kernel@...r.kernel.org, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, keith.busch@...el.com
Subject: Re: [PATCH RESEND] PCI/AER: Use a common function to print AER error
 bits



On 04/30/2018 12:15 PM, Bjorn Helgaas wrote:
> On Sat, Apr 28, 2018 at 12:07:48PM -0500, Alex G. wrote:

(snip)
>> I could update the offending line to say:
>>  +	info.first_error = PCI_ERR_CAP_FEP(aer->cap_control);
> 
> That's what I would have expected.  So I'd say either do this, or add
> a comment about why it's not the right thing to do.

Okay.

>> Though I still have the concerns with validating CPER data:
>>
>>> I can see a way to use even more common printk code, but that requires
>>> validating the PCI regs we get from firmware. That means we need to make
>>> a guarantee about CPER that is beyond the scope of this patch.
> 
> Sounds like this is material for another patch, but if/when you do
> that, I'd like to understand your concern about validating the
> registers we get from firmware.  Are you worried about getting
> incorrect register contents, then printing the wrong info, making
> the wrong decision about how to recover, something else?

I don't trust firmware, and I have daymares about firmware leaving these
fields uninitialized. In jargon, I'd like to treat it as external
untrusted serialized data.

Alex